Mercury switch



Dec. 9, 1941. P. s. BEAR ETAL 2,265,681,

. MERCURY SWITCI-L v Filed 001:. 4, 1939 2 Sheets-Sheet 1 Dec. 9, 1941. P. s. BEAR EIAL. 2, 65, 8

MERCURY SWITCH Filed Oct. 4, 1939 I 2 Sheets-Sheet 2 ATTORNEY,

erald Z Patented D c. 9, 1941 MERCURY SWITCH Paul S. Bear and Gerald E. Spates, Elkhart, Ind., assignors to Bucklen-Bear Laboratories, Inc., Iflkhart, Ind., a corporation of Indiana Application October 4, 1939, Serial No. 297,805

16 Claims.

This invention relates to mercury switches, and more particularly is-directed to mercury switches of the metal envelope type to be employed in low voltage circuits such. as used in automobile light systems and the like.

Mor particularly, the present invention is directed to switches adapted to'operate on battery currents used for lighting the interiors of compartments, such as trunk compartments, glove compartments, and engine compartments of vehicles, the switches being attached to the hinged cover closing such compartments and being tilted into switch operating position upon opening of such cover.

One of the primary objects of the present invention is to design a. switch that will be extremely simple to assemble, will comprise relatively few parts, and will be capable of mass production at very small cost. In this connection we have designed a switch of the general type shown in the copending application of Paul S. Bear, Serial No. 745,842, filed September 28, 1934.

The present invention contemplates the provision of a metal envelope which is preferably cup-shaped, and at its open end is provided with a counterbored portion forming an internal radial shoulder or tapered seat. Seated in this end is an insulating plug carrying an electrode which projects outwardly of the end thereof. The plug is suitably compressed into sealing engagement with the envelope wall by spinning over the end of the envelope, or spinning the envelope into a groove in the plug, and the shank of the electrode is insulated by the plug radially with respect to the metallic envelope. Plugs of this type can be formed in multiple cavity molds and can therefore be produced very economically, while the switch envelopes can be screw machined parts which are also capable of economical production. The electrode carried by the insulating plug can comprise an ordinary nail, or a cold headed shank piece. of suitable length and size with the head end thereof forming the contact surface against which the body of mercury is adapted to' engage. This nail is preferably driven through the plug in such manner as to be tightly gripped therein, and preferably, the shank of the nail is of the type that is corrugated or finned to insure locking en agement of .the' shank within the plug. From the above it will be apparent that the production of the switch can be made very economically and that the assembly is very much simplifled,-as compared to the normal types of metal envelope mercury switches.

Other objects and advantages of thepresent invention will be more apparent from the following detailed description which, taken in conjunction with the accompanying drawings, will disclose to those skilled in the art the particu-- lar construction and operation of a preferred form of the invention.

In the drawings:

Figure l is an exploded view taken on the transverse section through the switch;

Figure 2 is a sectional view showing the switch in its off" position;

Figure 3 is a corresponding view showing the switch in its on position;

Figure 4 is an end elevation of a slightly modified construction;

Figure 5 is a sectional view through a modified form of switch having a tapered plug seat;

Figure 6 is a similar view of a still further modified form of switch;

Figures 7 to 9, inclusive, are similar views showing different means for holding the plug in position in the envelope;

Figure 10 is an elevational view of the clamping ring employed in Figure 9;

Figure 11 is a sectional view of a still further modified form of the invention; and

Figure 12 is a corresponding view of a still further modified form of switch.

Considering now the drawings in detail, we provide a switch envelope 5 which may be formed of iron or steel, and which, at its open end is provided with a counterbored portion 1 forming the radially extending shoulder 6 with the main body portion of the switch.

In manufacturing the switch, a body of mercury 8 is first introduced therein, and over this is disposed a body of alcohol 9, it being understood that prior to this, all parts of the switch have been thoroughly washed in alcohol or any other suitable medium to remove any impurities or foreign matter therefrom. .When the mercury and alcohol in the proper quantities have been introduced-into the switch envelope 5, the ring it is pressed in position on the shoulder 8 forming a stop for limiting the inward movement of the insulating plug 12.

The plug I2 is preferably formed of rubber which has been molded into shape, and is a substantially unitary hard mass with limited elastic properties. We have found that rubber of the type used in the mallet heads of rubber mallets has the desired characteristics for the purposes or other liquid fills of the type contemplated at the temperature at which these switches oper ate. Such rubber-is molded so that its outside diameter is very slightly greater than the counterbored portion 1 of the envelope 5.. By means 1 thereof projects from the inner face of the plug. With the plug and electrode thus in position in the end I of the switch, the shank of the electrode is radially insulated from the envelope wall by means 'of the cylindrical extension IS on the plug which projects outwardly a distance suflicient to insure that there can be no direct leakage path between the shank and the envelope wall.

, After the electrode and plug have thus been positioned, the ring I6 is applied about the outer face of the plug l2, having an inner diameter such that it is spaced from the extension i 5 and pressure is applied thereon to slightly bulge the rubber plug l2 to insure its sealing engagement with the surface I of the envelope. "The outer edge of the envelope indicated at I! is then spun over, thereby holding the parts in compressed sealed engagement in the end of the envelope and preventing any leakage past the rubber or electrode. The retaining rings Ill and i6 are employed for the purpose of preventing bulging of the rubber when the spinning pressure is applied, and also preventing any possible shearing of the rubber on the shoulder 6 of the envelope. When the switch hasthus been sealed, it is in condition for operation, it being understood that no evacuation of the interior of the switch is provided since we have found that the alcohol, or a liquid fill such as triethanolamine, is sufficient to pick up contamination withinthe switch, leaving the mercury clean and allowing no deposits of mercury globules which might hold the circuit closed. Also, thealcohoi and rubber are of such I 7 2,265,681 which we require, and is not aifected by alcohol ring i0 is replaced by a ceramic or refractory washer which extends entirely across the face of the plug 1 and is seated against the shoulder 6 formed in the envelope 5. The outer-end of the envelope issealed in the manner previously described to retain theplug in compressed position between the washer 20 and the washer l6.

In this form of the invention it is contemplated that the-switch envelope may be evacuated, and for this purpose, the electrode I3 is disposed in inverted position, that is, it is driven through the plug and through the washer 20 from the outer end of the envelope, after the envelope has been evacuated and filled through character that there is no interaction therebetween which might tend to destroy the switch.

With the switch in the position shown in Figure 2, it will be apparent that the body of mercury 8 is entirely out of contact with the electrode head l3, and the circuit through the switch connected thereto by the conductors lBand l9 secured respectively to the shell 6 and to the shank of the electrode i2 is open. When the switch is tilted from the position shown in Fig-. ure 2 to that shown in Figure 3 the body of mercury 8 moves longitudinally within the'envelope 5 to provide for bridging contact between the envelope 5 and the electrode head I. This completes thecircuit through the switch, and this circuit will remain closed 'until the envelope is again tilted in the opposite direction.

In Figure 4 we provide for retaining the plug incompressed position by staking over only cer- I of switch construction as compared with that shown in Figures 1 to 4, in which the metallic the opening in the plug 1 which the shank l3 of the electrode is adapted to close. This opening in the plug 1 is of smaller diameter than the shank I3, but is sufilciently large to allow evacuation and filling of the shell after the plug has been compressed into sealedvengagement with the end of the envelope. When the nail like electrode is then driven through the plug, it expands the opening intotight sealing engagement with the lateral surface thereof and the tip end portion 22 extends inwardly of the refractory 20 to provide an electrode spaced from the shell with which the body of mercury is adapted to make contact when the switch is tilted into the position'shown in Figure 5.

Considering now the form of the invention shown in Figure 6. this is similar to that described in connection with Figurev 5, except that the envelope 5' is provided with a frusto-conical outer end portion 24 forming a wedge-shaped opening into which the tapered plug 25 is adapted to be pressed, the plug under such pressure formv ure 5, and is adapted to be. driveninto place after the mercury 8 and liquid fill 9 have been introduced into the envelope through the opening through which the electrode is driven.

In Figure-,7 we have provided a metal envelope 30 which has inserted in the open end thereof the plug 32 provided with an annular recessed surface 33. The plug 32 which is of resilient insulating material when introduced into the envelope at a distance such that the outer face thereof is flush withthe end of the envelope, is locked in position by spinning an inwardly directed bead 34 into the envelope shell about the groove 33. This effectively locks the plug against axial movement in either direction and the envelope may then be filled with mercury 8 and liquid 9 and then completely closed by means of the electrode 35 being driven through the contact the plug in the manner shown. This provides a very simple type of switch in which no counterboring in the envelope or successive drawing operations thereon are required, and the spinning operation may be readily accomplished at little or no cost.

In Figure 8 a still further modified construction is provided in which the envelope 40 is provided with an annular groove 42 formed in the internal surface thereof adjacent the open end. A substantially straight insulating plug 43 is provided which is pressed into the open end of the envelope, and which has the central opening '44 therein adapted to receive the shank of the electween said envelope and 6. A mercury switch comprising an elongated cup-shaped shell, an insulating plug adapted to be pressed axially inwardly tovseat in said shell for closing the open end thereof, a nail extending axially through said plug and having a head at one end thereof, the end of the shell being spun inwardly of the inner face thereof, and a of mercury in the envelope adapted to engage electrode upon tilting of said switch.

.12. In a mercury switch, a cup-shaped metal envelope having an internal radial abutment ad-" 'jacent the open endthereof, a semi-rigid insuover intermediate .the ends of said plug to re- 5 .tain the ,plug against outward movement, anda body of mercury in the shell.

7. A switch comprising a cup-shaped metal envelopeadapted to contain a body of mercury and having a counterbored open end forming an internal radial shoulder, a metallic ring seated on said shoulder and projecting radially inwardly thereof, an insulating semi-elastic plug fitting tightly in'said counterbored portion and abutting against said ring, a nail driven axially through said plug with the head on the inner? face thereof spaced radially from said ring, a second ring on the opposite face of said plug and seated in the end of the envelope, said end being spun over said second ring to impose axial pressure thereon for radially sealing said plug against the confining surface of said envelope, and a 1 the outer washer fitting under the spun over end of the envelope, a nail-like electrode extending centrally through the plug and having its head spaced radially from the inner washer, and a body of mercury in the envelope adapted to make and break contact between said head and envelope upon tilting of the envelope.

9. A mercury switch comprising an elongated cup-shaped shell, 9. semi-resilient insulating plug closing the open end thereof, an electrode extendingaxially through said plug, the shell being deformed radially intermediate the ends of said plug to. retain the plug. against outward movement, and a body of mercury in the shell.

10. A mercury switch comprising a cup-shaped metal envelope having an open end provided with an internal annular recess, a resilient insulating plug pressed into said end, an electrode having a shank portion adapted to-be forced ax- .ially through said plug, a portion of said-plug being adapted tobe expanded into locking engagement within said recess upon said movement of said shankportion, and a body of mercury movable into and out of bridging contact beelectrode upcn tilting of saidswitch.

11. A mercury comprising soup-shaped metal envelope having an open end, a semisilientinsulatingnlugextendingintosaidopen end, an annular ring-like portion of said enlating plug seated in said open end. an electrode pin extending axially through said plug and having' the ends thereof projecting from opposite end; of the plug, the peripheral edge of the envelo'pe being spun over the outer face of said plug to maintain it in position, said plug having an integral cylindrical extension radially insulating said in from said spun-over edge, and a body of mercury in said'envelope adapted to make and break contact with the i'nnerproiecting end of said pin upon movement of said mercury axially inv said envelope.

13. The switch of claim 12 further characterized in that said plug has a facing of ceramic insulating material on the inner end face there- 14. Incombination, a cup-shaped metallic shell,

an insulating plug driven-into the open end of said shell into sealing engagement therewith, an electrode pin driven axially through said plug until the inner end projects beyond the inner face of said plug, said shell having a radially in--- struck portion intermediate the ends of said plug for interlocking the plug and shell against relative axial movement, and a body of mercury in said shell movable axially into engagement with said end of said Pin- 15. The. combination, with a metallic cupshaped shell having an internal enlargement adjacent the open end defining a radial shoulder,-

f an end assembly comprising a semi-ri id insulating plug having end washers adapted to be inserted'into said' end and stopped against said shoulder, the edge of the envelope being spun over the outer washer; an electrode extending centrally through said plug and radially spaced from said washers, and a reduced cylindrical extension on the outer end of said plug radially insulating the electrode shank from the outer washer and the spun-over edge.

16. Incombination, a cup-shaped tubular metal envelope having a uniform external diameter and having a counterbore in the open end thereof Q providing a radial shoulder internally of said end, a solidsemi-resilient cylindrical plug of substantially uniform diameter seated in said counterbored portion and seating against said shoulder to limit inward movement thereof, an electrode pin extending axially through said plug and projecting from opposite ends thereof, a reduced cylindrical extension on said plug extending axially beyond the end of the envelope about said pin, a body of mercury in said envelopefor makim and breaking the circuit between said velope andpin. a washer engaging said plug about'said extension, and radially inturned means integral with the end of said envelope en-' vel'opebeing mminwardly the ends of said plug to deform 881d P 8 I01 locking laid plug and envelope against relative movement,v anele'ctrode carried in said plugand pr j the-outer face of washer for locking said plug and washer against outward movement.-

PAUL S. BEAR GERALD E. srlrms. 

